Iron-tanned leather and process of making same



Patented Oct. 31, 1939 PATENT OFFICE I IBON- TANNEfi LEATHER AND PROCESSOF MAKING SAME Ludwigshafen-on-thee-Bhine, assignor to I. G.Farbenindustrie Aktlengescllschaft, Frankfort-on-the-Main, Ger- WernerHuehn,

many

No Drawing.

Application March 19, 1938, Se-

rialNo. 196,905. In Germany March 22, 1937 10 Claims.

The present invention relates to a new process of tanning hides by meansof tanning agents containing iron.

I have found that excellent leather having a firm, smooth grain and asoft, full touch is obtained by treating hides with solutions of suchmononuclear or, advantageously, polynuclear iron complex compounds asare capable of having acid radicals enclosed in the secondfsphere oftheir complex, in the presence of acids capable of being so enclosed ortheir watersoluble salts.

For the said enclosure, or adding on,-there may be mentioned aliphatichydroxy acids, such as glycolic acid and polybasic, in particulardibasic, acids or their watersoluble salts, as for example sulphuricacid, malonic acid, tartaric acid, citricacid, oxalic acid, phthalicacid and their salts. Phosphoric acid and its salts, as for examplesecondary sodium phosphate, may also be used with advantage. As ironcomplex compounds which are capable of forming two-shell complexes inthe said manner, there may be mentioned for example those formed by thereaction of iron chloride with alkali salts of weak organic acids, asfor example formic acid, acetic acid, hydroxyacids, such as lactic acid,and amino acids, in aqueous solution, for example the nitrogenouscomplex salts to be used according to the application Serial No. 90,918,filed on July 16th, 1936, now Patent No. 2,122,133.Hexaacetato-dihydroxy-tri ferric salts andhexaformiato-dihydroxy-triferric salts are also suitable.

By the enclosure of the acid radical within the complex, compounds areoften formed in which the iron complex has a charge opposite to thatwhich it had in the complex compound originally employed. For examplefrom the cationic hexaacetato-dihydroxy-triferric base having a singlepositive charge:

there is obtained by the enclosure of four sulphate radicals in thesecond sphere, an acid having seven negative charges and having thecomposi-- tion:

(CHiO O0) 7-- [Fan 04):

enclosed in the second sphere of the complex is Y advantageously used insuch an amount that the ratio of the complex iron acid and base presentin the tanning liquor corresponds approximately to the ratio of thebasic and acid places of the hide.

The acids or salts capable of being enclosed in the second sphere may beadded to the original cationic iron complex salts in the tanning liquoritself, or these and also the anionic two-shell complex salts may beallowed'to form by mutual dis solution of the components in the tanningliquor.

It is also possible to enclose different salts and acids simultaneouslyand to allow diiferent cationic iron complex salts to react.

It is preferable to allow the two-shell complex anions and the one-shellcomplex cations to act on the hides in such amounts as correspond to theproportion of basic and acid spots in the hides.

Tanning by the said process takes place rapidly and uniformly; theunhaired hides generally speaking need not be neutralized after thetanning because they are stable to plumping by hot water directly afterthe tanning. After rinsing with warm water they may be fat-liquored withthe usual fat emulsions and prepared in the usual manner, as for exampleas russet leather. The leather dries soft and full. If desired theresulting leather may be further treated with aftertreatment agentsgenerally used in tanning.

The following examples will further illustrate the nature of thisinvention but the invention is not restricted to these examples. Theparts are by weight.

' Example 1 100 parts of unhaired cattle hides which have been pickledin the usual manner are moved in the vat with a solution of 100 parts ofwater, 12 parts of hexa-acetato-dihydroxy-bicarbamidotriferric chloride,3 parts of anhydrous sodium sulphate and 1 part of sulphuric acid of 66Baum strength until the unhaired hides have been completely tannedthrough. This operation takes from 8 to 20 hours depending on thethickness of the unhaired hides. A leather of uniform section isobtained having a firm, smooth grain which without aftertreatmentpossesses the valuable property of not plumping. After storingovernight, the leather is rinsed in water at 30 C.-

for fromhalf an hour to an hour, fatted and prepared as russet leatherin the usual manner. The leather thus obtained dries very soft and has abeautiful pale colour.

Example 2 parts of unhaired cattle hides which have been pickled in theusual manner are drummed with a solution of 5.7 parts of anhydrous ironchloride, 5.8 parts of anhydrous sodium acetate, 2.5 parts of urea, 3.5parts of anhydrous sodium sulphate and 1 part of .sulphuric acid of 66Baum strength in 100 parts of water until complete tanning through iseffected. The leather is rinsed, fatted and prepared directly aftertanning. A leather similar to that in Example 1 is obtained.

Example 3 100 parts of unhaired cattle hides which have been pickled inthe usual manner are drummed for from 8 to 20 hours with a solution of12 parts of hexa acetato dihydroxy bicarbamido-triferric chloride, 3parts of potassium oxalate and 0.5 part of sulphuric acid of 66 Baumstrength in 100 parts of water. After tanning through, the leather isstored for a day, rinsed for half an hour at 30 C., fatted and preparedin the usual manner, a leather having a beautiful pale colour beingobtained.

Example 4 The procedure described in Example 3 is followed, except thatthe potassium oxalate is replaced by 3.5 parts of secondary sodiumphosphate. After rinsing, fatting and preparation, a leather is obtainedwhich is very full especially in the sides.

Example 5 100 parts of unhaired calf hides which have been pickled with0.7 part of sulphuric acid of 66 Baum strength drummed in the vat for 8hours with a solution of 8 parts ofhexa-acetato-dihydroxy-tricarbamido-triferric chloride, 2 parts ofsodium phthalate and 0.5 part of sulphuric acid of 66 Baum strength in100 parts of water. After the said time the unhaired hides have beentanned through with the exhaustion of the tanning liquir. After rinsing,fatting and softening,

' the leather dries soft.

Example 6 100 parts of calf hides pickled in the usual manner with 0.7per cent of sulphuric acid are drummed with 100 per cent of water, 5 percent of sodium chloride, 12 per cent ofhexa-acetatodihydroxy-bicarbamido-triferric chloride and 1.5 per cent ofglycolic acid until the taning is complete. Then neutralization iseifected with 2.9 per cent of sodium carbonate. The leather is washedwith water, fat-liquored and finished in the usual manner. The leatherpossesses a good resistance to hot water (shrinkage 5 per cent).

What I claim is:

1. The process for the production of leather, which comprises treatinghides with a solution of an iron complex compound capable of havingacidradicals enclosed in the second sphere of its complex, in thepresence of a substance selected from the class consisting of the acidscapable of being so enclosed and the water-soluble salts of such acids.

2. The process forthe production of leather. which comprises treatinghides with a solution of a polynuclear iron complex compound capable ofhaving acid radicals enclosed in the second sphere of its complex, inthe presence of a substance selected from the class consisting of theacids capable of being so enclosed and the watersoluble salts'of suchacids.

3. The process for the production of leather, which comprises treatinghides with a solution of a hexaacetato-dlhydroxy-triierric salt and asubstance selected from the class consisting of polybasic acids,aliphatic hydroxy acids and the water-soluble salts of the said acids.

4. The process for the production of leather, which comprises treatinghides with a solution of a hexaacetato-dihydroxy-bicarbamido-triferricsalt and a substance selected from the class consisting of polybasicacids, aliphatic hydroxy acids and the water-soluble salts of the saidacids.

5. The process for the production of leather.

which comprises treating hides with a solution of ahexaacetato-dihydroxy-tricarbamido-triferric salt and a substanceselected from the class consisting of polybasic acids, aliphatic hydroxyacids and the water-soluble salts of the said acids.

6. Leather tanned with an iron complex compound capable of having acidradicals enclosed in the second sphere of its complex and a substanceselected from the class consisting of the acids capable of being soenclosed and the watersoluble salts of such acids.

7. Leather tanned with a polynuclear iron complex compound capable ofhaving acid radicals enclosed in the second sphere of its complex and asubstance selected from the class consisting of the acids capable ofbeing so-enclosed and the water-soluble salts of such acids.

8. Leather tanned with a hexaacetato-dihydroxy-triferric salt and asubstance selected from the class consisting of'poly-basic acids,aliphatic hydroxy acids and the water-soluble salts of the said acids.

9. Leather tanned with a hexaacetato-dihydroxy-bicarhamido-triferricsalt and a substance selected from the class consisting of polybasicacids, aliphatic hydroxy acids and the water-soluble salts of the saidacids.

10. Leather tanned with a hexaacetato-dihydroxy-tricarbamido-triferricsalt. and a substance selected from the class consisting of polybasic'acids, aliphatic hydroxy acids and the watersoluble salts ofs the saidacids.

WERNER HUEHN.

